As the threat of a scarcity of energy becomes more real than apparent, there is increasing interest in new, often exotic sources of energy. Ironically, at the same time many individuals are returning to older, proven sources of energy which have fallen into disfavored during the era of cheap and abundant petroleum fuels. The most notable of these more traditional energy sources is firewood, a fuel source which is renewable, easy to burn, and pleasing to use.
A major criticism of the use of firewood has been that although many homes are provided with fireplaces for wood burning, the fireplace exhibits very low efficiency in converting the potential energy of the wood into useful energy in the home. It is estimated that as much as 90 percent of the heat energy of a wood burning fire in a fireplace escapes up the chimney, the remainder being radiated into the adjacent room to provide heat therefore.
The low efficiency of most wood burning fireplaces is due to the face that a fireplace relies almost exclusively upon radiation to convey heat from the fire to the room. The most efficient radiator is the hottest part of the fire. Unfortunately, the hottest part of the fire is often found at the center of the burning mass of wood, with the outer portions of the burning wood blocking the radiation which might otherwise heat the adjacent room.
Attempts have been made in the prior art to construct devices which extract more useful heat from a fireplace. These devices include arrangements for circulating room air through conductors which pass through the fireplace, as well as devices which structure the fire so that the hottest burning portion is disposed to radiate directly into the adjacent room. However, the latter group of prior art devices often rely on the logs themselves to form the desired burning configuration. As the logs are consumed by the combustion process, they must be continually rearranged to provide the optimum radiating configuration.
The following U.S. Pat. Nos. represent the prior art most pertinent to the present invention: 3,505,986; 3,612,034; 4,069,808.